Methods and apparatus for position sensitive suspension damping

ABSTRACT

An apparatus and system are disclosed that provide position sensitive suspension damping. A damping unit includes a piston mounted in a fluid-filled cylinder. A vented path in the piston may be fluidly coupled to a bore formed in one end of the piston rod, creating a flow path for fluid to flow from a first side of the piston to a second side of the piston during a compression stroke. The flow path may be blocked by a needle configured to engage the bore as the damping unit is substantially fully compressed, thereby causing the damping rate of the damping unit to increase. In one embodiment, the piston includes multiple bypass flow paths operable during the compression stroke or the rebound stroke of the damping unit. One or more of the bypass flow paths may be restricted by one or more shims mounted on the piston.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and is a Continuation of the patentapplication Ser. No. 14/506,420, entitled “METHODS AND APPARATUS FORPOSITION SENSITIVE SUSPENSION DAMPING,” with filing date Oct. 3, 2014,by Everet Owen Ericksen et al., which is incorporated herein, in itsentirety, by reference.

The application with Ser. No. 14/506,420 claims priority to and is aDivisional of the patent application Ser. No. 13/485,401, entitled“METHODS AND APPARATUS FOR POSITION SENSITIVE SUSPENSION DAMPING”, withfiling date May 31, 2012, by Everet Owen Ericksen et al., which isincorporated herein, in its entirety, by reference.

The application with Ser. No. 13/485,401 claims priority to the patentapplication, Ser. No. 61/491,858, entitled “METHODS AND APPARATUS FORPOSITION SENSITIVE SUSPENSION DAMPING”, with filing date May 31, 2011,by Everet Owen Ericksen et al., which is incorporated herein, in itsentirety, by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates generally to vehicle suspensions and, morespecifically, to variable damping rates in vehicle shock absorbers andforks.

Description of the Related Art

Vehicle suspension systems typically include a spring component orcomponents and a damping component or components. Often, mechanicalsprings, like helical springs, are used with some type of viscousfluid-based damping mechanism, the spring and damper being mountedfunctionally in parallel. In some instances a spring may comprisepressurized gas and features of the damper or spring areuser-adjustable, such as by adjusting the air pressure in a gas spring.A damper may be constructed by placing a damping piston in afluid-filled cylinder (e.g., liquid such as oil). As the damping pistonis moved in the cylinder, fluid is compressed and passes from one sideof the piston to the other side. Often, the piston includes ventsthere-through which may be covered by shim stacks to provide fordifferent operational characteristics in compression or extension.

Conventional damping components provide a constant damping rate duringcompression or extension through the entire length of the stroke. As thesuspension component nears full compression or full extension, thedamping piston can “bottom out” against the end of the damping cylinder.Allowing the damping components to “bottom out” may cause the componentsto deform or break inside the damping cylinder.

As the foregoing illustrates, what is needed in the art are improvedtechniques for varying the damping rate including to lessen the risk ofthe suspension “bottoming out.”

SUMMARY OF THE INVENTION

One embodiment of the present disclosure sets forth a vehicle suspensiondamper that includes a cylinder having a compression chamber and arebound chamber and containing at least a portion of a piston rod havinga piston attached thereto, where an outer diameter of the piston engagesan inner diameter of the cylinder and is relatively movable therein, andwhere the piston borders each of the compression chamber and the reboundchamber. The vehicle suspension damper further includes a damping liquidwithin the cylinder and a bypass fluid flow path connecting thecompression chamber and the rebound chamber, which forms a fluid pathextending between an inner diameter of the piston and a side surface ofthe piston directly bordering one of the compression or reboundchambers.

Another embodiment of the present disclosure sets forth a vehiclesuspension damper that includes a cylinder and a damping liquid withinthe cylinder, the cylinder having a compression chamber and a reboundchamber and containing at least a portion of a piston rod having apiston attached thereto, where an outer diameter of the piston engagesan inner diameter of the cylinder and is relatively movable therein, andwhere the piston borders each of the compression chamber and the reboundchamber. The piston includes multiple flow paths that enable the dampingliquid to flow from the compression chamber to the rebound chamber. Themultiple flow paths include a damping flow path that comprises a firstfluid path extending between a first side surface of the piston directlybordering the compression chamber and a second side surface of thepiston directly bordering the rebound chamber and a bypass flow paththat comprises a fluid path extending between an inner diameter of thepiston and one of the first side surface of the piston or the secondside surface of the piston.

Yet another embodiment of the present disclosure sets forth a vehiclesuspension system that includes a first damper unit. The first damperunit includes a cylinder having a compression chamber and a reboundchamber and containing at least a portion of a piston rod having apiston attached thereto, wherein an outer diameter of the piston engagesan inner diameter of the cylinder and is relatively movable therein, andwherein the piston borders each of the compression chamber and therebound chamber. The first damper unit further includes a damping liquidwithin the cylinder and a bypass fluid flow path connecting thecompression chamber and the rebound chamber, which forms a fluid pathextending between an inner diameter of the piston and a side surface ofthe piston directly bordering one of the compression or reboundchambers.

One advantage of some disclosed embodiments is that multiple bypass flowpaths enable the vehicle suspension damper to be setup such that thedamping rate changes (i.e., is increased) as the damper nears fullcompression. The increased damping rate, caused by fluid being forcedthrough fewer flow paths formed by the multiple bypass flow paths causesthe force opposing further compression of the damper to increase,thereby decreasing the chance that the damper “bottoms out.”

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features can be understoodin detail, a more particular description, briefly summarized above, maybe had by reference to certain example embodiments, some of which areillustrated in the appended drawings. It is to be noted, however, thatthe appended drawings illustrate only typical embodiments and aretherefore not to be considered limiting the scope of the claims, whichmay admit to other equally effective embodiments.

FIG. 1 shows an asymmetric bicycle fork having a damping leg and aspring leg, according to one example embodiment;

FIGS. 2A-2C show sectional side elevation views of a needle-typemonotube damping unit in different stages of compression, according toone example embodiment;

FIG. 3 shows a detailed view of the needle and bore at the intermediateposition proximate to the “bottom-out” zone, according to one exampleembodiment;

FIGS. 4A and 4B illustrate the castellated or slotted valve, accordingto one example embodiment;

FIGS. 5A and 5B illustrate a damping unit having a “piggy back”reservoir, according to one example embodiment;

FIG. 6 illustrates a half section, orthographic view of a damping unit,according to another example embodiment;

FIGS. 7A through 7E illustrate the piston of FIG. 6 , according to oneexample embodiment; and

FIGS. 8A and 8B illustrate the shaft of FIG. 6 , according to oneexample embodiment.

For clarity, identical reference numbers have been used, whereapplicable, to designate identical elements that are common betweenfigures. It is contemplated that features of one example embodiment maybe incorporated in other example embodiments without further recitation.

DETAILED DESCRIPTION

Integrated damper/spring vehicle shock absorbers often include a damperbody surrounded by or used in conjunction with a mechanical spring orconstructed in conjunction with an air spring or both. The damper oftenconsists of a piston and shaft telescopically mounted in a fluid filledcylinder. The damping fluid (i.e., damping liquid) or damping liquid maybe, for example, hydraulic oil. A mechanical spring may be a helicallywound spring that surrounds or is mounted in parallel with the damperbody. Vehicle suspension systems typically include one or more dampersas well as one or more springs mounted to one or more vehicle axles. Asused herein, the terms “down”, “up”, “downward”, “upward”, “lower”,“upper”, and other directional references are relative and are used forreference only.

FIG. 1 shows an asymmetric bicycle fork 100 having a damping leg and aspring leg, according to one example embodiment. The damping legincludes an upper tube 105 mounted in telescopic engagement with a lowertube 110 and having fluid damping components therein. The spring legincludes an upper tube 106 mounted in telescopic engagement with a lowertube 111 and having spring components therein. The upper legs 105, 106may be held centralized within the lower legs 110, 111 by an annularbushing 108. The fork 100 may be included as a component of a bicyclesuch as a mountain bicycle or an off-road vehicle such as an off-roadmotorcycle. In some embodiments, the fork 100 may be an “upside down” orMotocross-style motorcycle fork.

In one embodiment, the damping components inside the damping leg includean internal piston 166 disposed at an upper end of a damper shaft 136and fixed relative thereto. The internal piston 166 is mounted intelescopic engagement with a cartridge tube 128 connected to a top cap180 fixed at one end of the upper tube 105. The interior volume of thedamping leg may be filled with a damping liquid such as hydraulic oil.The piston 166 may include shim stacks (i.e., valve members) that allowa damping liquid to flow through vented paths in the piston 166 when theupper tube 105 is moved relative to the lower tube 110. A compressionchamber is formed on one side of the piston 166 and a rebound chamber isformed on the other side of the piston 166. The pressure built up ineither the compression chamber or the rebound chamber during acompression stroke or a rebound stroke provides a damping force thatopposes the motion of the fork 100.

The spring components inside the spring leg include a helically woundspring 115 contained within the upper tube 106 and axially restrainedbetween top cap 181 and a flange 165. The flange 165 is disposed at anupper end of the riser tube 135 and fixed thereto. The lower end of theriser tube 135 is connected to the lower tube 111 in the spring leg andfixed relative thereto. A valve plate 155 is positioned within the upperleg tube 106 and axially fixed thereto such that the plate 155 moveswith the upper tube 106. The valve plate 155 is annular inconfiguration, surrounds an exterior surface of the riser tube 135, andis axially moveable in relation thereto. The valve plate 155 is sealedagainst an interior surface of the upper tube 106 and an exteriorsurface of the riser tube 135. A substantially incompressible lubricant(e.g., oil) may be contained within a portion of the lower tube 111filling a portion of the volume within the lower tube 111 below thevalve plate 155. The remainder of the volume in the lower tube 111 maybe filled with gas at atmospheric pressure.

During compression of fork 100, the gas in the interior volume of thelower tube 111 is compressed between the valve plate 155 and the uppersurface of the lubricant as the upper tube 106 telescopically extendsinto the lower tube 111. The helically wound spring 115 is compressedbetween the top cap 181 and the flange 165, fixed relative to the lowertube 111. The volume of the gas in the lower tube 111 decreases in anonlinear fashion as the valve plate 155, fixed relative to the uppertube 106, moves into the lower tube 111. As the volume of the gas getssmall, a rapid build-up in pressure occurs that opposes further travelof the fork 100. The high pressure gas greatly augments the spring forceof spring 115 proximate to the “bottom-out” position where the fork 100is fully compressed. The level of the incompressible lubricant may beset to a point in the lower tube 111 such that the distance between thevalve plate 155 and the level of the oil is substantially equal to amaximum desired travel of the fork 100.

FIGS. 2A-2C show sectional side elevation views of a needle-typemonotube damping unit 200 in different stages of compression, accordingto one example embodiment. In one embodiment, the components included indamping unit 200 may be implemented as one half of fork 100. In anotherembodiment, damping unit 200 may be implemented as a portion of a shockabsorber that includes a helically-wound, mechanical spring mountedsubstantially coaxially with the damping unit 200. In yet otherembodiments, damping unit 200 may be implemented as a component of avehicle suspension system where a spring component is mountedsubstantially in parallel with the damping unit 200.

As shown in FIG. 2A, the damping unit 200 is positioned in asubstantially fully extended position. The damping unit 200 includes acylinder 202, a shaft 205, and a piston 266 fixed on one end of theshaft 205 and mounted telescopically within the cylinder 202. The outerdiameter of piston 266 engages the inner diameter of cylinder 202. Inone embodiment, the damping liquid (e.g., hydraulic oil or other viscousdamping fluid) meters from one side to the other side of the piston 266by passing through vented paths formed in the piston 266. Piston 266 mayinclude shims (or shim stacks) to partially obstruct the vented paths ineach direction (i.e., compression or rebound). By selecting shims havingcertain desired stiffness characteristics, the damping effects can beincreased or decreased and damping rates can be different between thecompression and rebound strokes of the piston 266. The damping unit 200includes an annular floating piston 275 mounted substantially co-axiallyaround a needle 201 and axially movable relative thereto. The needle 201is fixed on one end of the cylinder 202 opposite the shaft 205. A volumeof gas is formed between the floating piston 275 and the end of cylinder202. The gas is compressed to compensate for motion of shaft 205 intothe cylinder 202, which displaces a volume of damping liquid equal tothe additional volume of the shaft 205 entering the cylinder 202.

During compression, shaft 205 moves into the cylinder 202, causing thedamping liquid to flow from one side of the piston 266 to the other sideof the piston 266 within cylinder 202. FIG. 2B shows the needle 201 andshaft 205 at an intermediate position as the damping unit 200 has justreached the “bottom-out” zone. In order to prevent the dampingcomponents from “bottoming out”, potentially damaging said components,the damping force resisting further compression of the damping unit 200is substantially increased within the “bottom-out” zone. The needle 201(i.e., a valve member) compresses fluid in a bore 235, described in moredetail below in conjunction with FIG. 3 , thereby drastically increasingthe damping force opposing further compression of the damping unit 200.Fluid passes out of the bore around the needle through a valve that isrestricted significantly more than the vented paths through piston 266.As shown in FIG. 2C, the damping rate is increased substantially withinthe “bottom-out” zone until the damping unit 200 reaches a positionwhere the damping unit 200 is substantially fully compressed.

FIG. 3 shows a detailed view of the needle 201 and bore 235 at theintermediate position proximate to the “bottom-out” zone, according toone example embodiment. As shown in FIG. 3 , the needle 201 issurrounded by a check valve 220 contained within a nut 210 fixed on theend of shaft 205. During compression within the “bottom out” zone, thevalve 220 is moved, by fluid pressure within the bore 235 and flow offluid out of bore 235, upward against seat 225 of nut 210 and the bulkof escaping fluid must flow through the annular clearance 240 thatdictates a rate at which the needle 201 may further progress into bore235, thereby substantially increasing the damping rate of the dampingunit 200 proximate to the “bottom-out” zone. The amount of annularclearance 240 between the exterior surface of the needle 201 and theinterior surface of the valve 220 determines the additional damping ratewithin the “bottom-out” zone caused by the needle 201 entering the bore235. In one embodiment, the needle 201 is tapered to allow easierentrance of the needle 201 into the bore 235 through valve 220.

During rebound within the “bottom out” zone, fluid pressure in the bore235 drops as the needle 201 is retracted and fluid flows into the bore235, causing the valve 220 to move toward a valve retainer clip 215 thatsecures the valve 220 within the nut 210. In one embodiment, the valveis castellated or slotted on the face of the valve 220 adjacent to theretainer clip 215 to prevent sealing the valve against the retainer clip215, thereby forcing all fluid to flow back into the bore 235 via theannular clearance 240. Instead, the castellation or slot allows amplefluid flow into the bore 235 during the rebound stroke to avoidincreasing the damping rate during rebound within the “bottom out” zone.The valve 220 is radially retained within the nut 210, which has arecess having a radial clearance between the interior surface of therecess and the exterior surface of the valve 220 that allows foreccentricity of the needle 201 relative to the shaft 205 without causinginterference that could deform the components of damping unit 200.

FIGS. 4A and 4B illustrate the castellated or slotted valve 220,according to one example embodiment. As shown in FIGS. 4A and 4B, thevalve 220 is a washer or bushing having an interior diameter sized tohave an annular clearance 240 between the interior surface of the valve220 and the exterior surface of the needle 201 when the needle 201passes through the valve 220. Different clearances 240 may be achievedby adjusting the interior diameter of the valve 220 in comparison to thediameter of the needle 201, which causes a corresponding change in thedamping rate proximate to the “bottom-out” zone. A spiral face groove ismachined into one side of the valve 220 to create the castellation orslot 230. It will be appreciated that the geometry of the slot 230 maybe different in alternative embodiments and is not limited to the spiraldesign illustrated in FIGS. 4A and 4B. For example, the slot 230 may bestraight (i.e., rectangular) instead of spiral, or the edges of the slot230 may not be perpendicular to the face of the valve 220. In otherwords, the geometry of the slot 230 creates empty space between thesurface of the retainer clip 215 and the surface of the valve 220 suchthat fluid may flow between the two surfaces.

When assembled, the valve 200 is oriented such that the side with theslot 230 is proximate to the upper face of the valve retainer clip 215,thereby preventing the surface of the valve 220 from creating a sealagainst the retainer clip 215. The slot 230 is configured to allow fluidto flow from cylinder 202 to bore 235 around the exterior surface of thevalve 220, which has a larger clearance than the annular clearance 240between the valve 220 and the needle 201. In one embodiment, two or moreslots 230 may be machined in the face of the valve 220. In someembodiments, the valve 220 is constructed from high-strength yellowbrass (i.e., a manganese bronze alloy) that has good characteristicsenabling low friction between the valve 220 and the needle 201. Inalternate embodiments, the valve 220 may be constructed from othermaterials having suitable characteristics of strength or coefficients offriction.

FIGS. 5A and 5B illustrate a damping unit 300 having a “piggy back”reservoir 350, according to another example embodiment. As shown in FIG.5A, damping unit 300, shown fully extended, includes a cylinder 302 witha shaft 305 and a piston 366 fixed on one end of the shaft 305 andmounted telescopically within the cylinder 302. Damping unit 300 alsoincludes a needle 301 configured to enter a bore 335 in shaft 305.However, unlike damping unit 200, damping unit 300 does not include anannular floating piston mounted substantially co-axially around theneedle 301 and axially movable relative thereto. Instead, the piggy backreservoir 350 includes a floating piston 375 configured to perform asimilar function to that of floating piston 275. A volume of gas isformed between the floating piston 375 and one end of the piggy backreservoir 350. The gas is compressed to compensate for motion of shaft305 into the cylinder 302. Excess damping liquid may enter or exitcylinder 302 from the piggy back reservoir 350 as the volume of fluidchanges due to ingress or egress of shaft 305 from the cylinder 302. InFIG. 5B, the damping unit 300 is shown proximate to the “bottom out”zone where needle 301 has entered bore 335.

FIG. 6 illustrates a half section, orthographic view of a damping unit400, according to another example embodiment. As shown in FIG. 6 ,damping unit 400 includes a piston 466 fixed on one end of a shaft 405and mounted telescopically within a cylinder 402. The shaft 405 includesa bore 435 that enables ingress of a needle (e.g., 201, 301) to changethe damping characteristics of the damping unit 400 proximate to the“bottom out” zone. The piston assembly includes a top shim stack 481 anda bottom shim stack 482 attached to the top face and bottom face of thepiston 466, respectively, which enable different damping resistances tobe set during the compression stroke and the rebound stroke. Duringoperation, where a needle has not entered bore 435, the damping liquidflows from one side of the piston 466 to the other side through multipleflow paths 451, 452, and 453. In compression, a first flow path 451(i.e., a damping flow path) allows the damping liquid to flow from anupper portion of the cylinder 402 through vented paths in the piston 466and into a lower portion of the cylinder 402, forcing the bottom shimstack 482 away from the bottom face of the piston 466. A second flowpath 452 (i.e., a bypass flow path) allows the damping liquid to flowfrom an upper portion of the cylinder 402 through the bore 435 and shaftports 440 in shaft 405 and into additional vented paths in the piston466 through the bottom shim stack 482 and into the lower portion of thecylinder 402. In rebound, a third flow path 453 (i.e., a rebound flowpath, not shown in FIG. 6 ) allows the damping liquid to flow from alower portion of the cylinder 402, through different vented paths in thepiston 466, through the top shim stack 481, and into an upper portion ofthe cylinder 402. In some embodiments, the first flow path 451 and thesecond flow path 452 may be associated with separate and distinct shimstacks. For example, the bottom shim stack 482 may be replaced by twoshim stacks configured in a clover pattern and arranged such that afirst shim stack covers the vented paths in the piston 466 correspondingto the first flow path 451 and a second shim stack covers the additionalvented paths in the piston 466 corresponding to the second flow path452.

When a needle just enters bore 435, the needle impedes the dampingliquid in the upper portion of the cylinder 402 from flowing through thesecond flow path 452 due to the “plugging” effect of the needle blockingthe entrance to the bore 435. However, the damping liquid may continueto pass through the piston 466 through the first flow path 451. Inaddition, some damping liquid may continue to flow out of ports 440 frombore 435 as the needle continues ingress into bore 435 and decreases thefluid volume inside the bore 435. It will be appreciated that thedamping rate will increase as the needle blocks the second flow path452, thereby forcing substantially all damping liquid in the upperportion of the cylinder 402 to move through piston 466 via the firstflow path 451. At some point during ingress of the needle, the fulldiameter of the needle is adjacent to the shaft ports 440, substantiallyblocking additional damping liquid from leaving bore 435 through theshaft ports 440. Again, the damping rate will increase as the needleblocks the shaft ports 440 and fluid pressure rapidly builds up withinbore 435 and acts on the needle to oppose any further compression of thedamping unit 400.

FIGS. 7A through 7E illustrate the piston 466 of FIG. 6 , according toone example embodiment. As shown in FIGS. 7A and 7B, the piston 466includes two vented paths (i.e., 421, 422) that allow damping liquid toflow from the upper portion of the cylinder 402 to the lower portion ofthe cylinder 402 via the first flow path 451 (i.e., bypassing the topshim stack and entering the piston 466 proximate to the inner surface ofcylinder 402). The piston 466 also includes two additional vented paths(i.e., 423, 424) that allow damping liquid to flow from the upperportion of the cylinder 402 to the lower portion of the cylinder 402 viathe second flow path 452 (i.e., through the bore 435 and shaft ports440). The additional vented paths are connected to the bore 435 viachannels 425 that fluidly couple the additional vented paths to theshaft ports 440 in shaft 405 through a surface on the inner diameter ofthe piston 466. The four vented paths described above (i.e., 421-424)allow damping liquid to flow from an upper portion of the cylinder 402to a lower portion of the cylinder 402 during a compression stroke. Inrebound, yet another set of four vented paths (i.e., 426, 427, 428, 429)allow damping liquid to flow from the lower portion of the cylinder 402to the upper portion of the cylinder 402 via the third flow path 453(i.e., bypassing the bottom shim stack 482 and passing into the upperportion of the cylinder 402 through the top shim stack 481). FIG. 7Cshows a side view of the piston 466 of FIGS. 7A and 7B. FIG. 7D shows across section of the piston 466 showing the inner diameter that is fitover shaft 405 as well as one channel 425 connected to one of theadditional vented paths in the piston corresponding to the first secondflow path 452. FIG. 7E shows a cross section of the piston 466 showingvented paths 423 and 424.

FIGS. 8A and 8B illustrate the shaft 405 of FIG. 6 , according to oneexample embodiment. As shown in FIGS. 8A and 8B, the shaft 405 includesa bore 435 formed (e.g., drilled, milled, etc.) into a top portion ofthe shaft. In one embodiment, the top portion of the shaft may have asmaller diameter than the body of the shaft 405, forming a seat aparticular distance from one end of the shaft 405. The piston assemblyincluding the piston 466 and the shim stacks may be mounted over the topportion of the shaft 405 and secured with a nut threaded onto the end ofthe shaft 405. In alternative embodiments, the nut may be press fit ontothe shaft 405 or secured in any other technically feasible manner.

Shaft ports 440 may be formed through an outer face of the top portionof the shaft 405 proximate a surface on the inner diameter of the piston466 when mounted on the shaft 405. The shaft ports 440 fluidly couplethe bore 435 in the shaft 405 with the additional vented paths (i.e.,423, 424) in the piston 466 such that fluid may flow through the bore435 via the second flow path 452. In other words, the second flow path452 enables additional fluid to flow through the bottom shim stacks 482when a needle is not blocking the bore 435.

It should be noted that any of the features disclosed herein may be usedalone or in combination. While the foregoing is directed to embodimentsof the present disclosure, other and further embodiments may beimplemented without departing from the scope of the disclosure, thescope thereof being determined by the claims that follow.

What we claim is:
 1. A vehicle suspension damper comprising: a cylindercontaining damping fluid and a piston assembly comprising: a piston; apiston rod; a first fluid path through said piston assembly and a secondfluid path through said piston assembly, said first fluid path and saidsecond fluid path for permitting damping fluid to pass from a first sideof said piston to a second side of said piston during a compressionstroke of said vehicle suspension damper; a valve member for resistingfluid flow through said second fluid path, wherein said valve member ismoved into a bore during compression and out of said bore duringextension, so as to displace at least some of said damping fluid throughsaid first fluid path and said second fluid path, and wherein said valvemember comprises a needle member sized to be inserted into said bore andwithdrawn from said bore, whereby a restriction to fluid flow throughsaid second fluid path is generated, said restriction being independentof pressure of said damping fluid caused by compression of said vehiclesuspension damper, said bore comprises a blind bore and, in use as saidvalve member is moved into said bore during compression said valvemember firstly begins to block said second fluid path, thereby forcingsaid damping fluid to flow through said piston via said first fluidpath, and secondly said valve member blocks said second fluid path,thereby blocking additional damping fluid from leaving said bore viasaid second fluid path such that fluid pressure builds up within saidbore to oppose any further compression of said damper; a floating pistonsurrounding said needle member; and a slotted, ring-shaped check valvefluidically coupled to said piston.
 2. The vehicle suspension damper ofclaim 1, wherein in use said restriction provided by said valve memberis dependent on a position of said suspension damper in said compressionstroke.
 3. The vehicle suspension damper of claim 1 wherein said valvemember is configured to enter said bore toward a maximum compression ofsaid suspension damper.
 4. The vehicle suspension damper of claim 1wherein said suspension damper is coupled to a vehicle.